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Thread: VNT's and BOV's

  1. #1
    Mitsu booster
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    VNT's and BOV's

    Hello all,

    Well I have a 89' CSX. VNT car. A while back I saw a 88 CSX at a junkyard and went to check it out. That CSX was actually in good shape but it had been stripped of drivetrain and anything that said "Shelby" on it. Anyways, in the trunk I found a great stock intake tube (way better than my duct taped tube) and a K&N filter, sweet! Scored a cold air intake for $3.50! I came home and cleaned up the super dirty filter and oiled it properly. I got some PCV pipe and made some tubes to connect it all.

    This is where the question comes. My stock air box does not have a BOV anywhere on it. From the intercooler to the TB it is a straight shot. and from the intake to the Turbo, also a straight shot. From my understanding, the VNT has a integrated BOV or waste-gate and closes/opens the vanes inside to adjust the pressure? I fabbed up the intake and slapped it on and took it for a drive. I was amazed, the little turbo is pretty loud and the BOV noise I am hearing is also decent. I was happy. From what I saw, it appeared that I didn't need a BOV. However, do I actually need one? O r could I benefit from one?

    TL;DR: Do VNT car's need BOVs?

    Pics of final intake setup:



    And the stock air box:






  2. #2
    Rhymes with tortoise. Turbo Mopar Staff cordes's Avatar
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    Re: VNT's and BOV's

    You're mistaking a blow off valve with a wastegate. The VNT doesn't have a wastegate due to its design. The 89 CSX didn't come with a BOV stock. It's not a bad idea at all to install a blow off valve on one IMO. The shaft speeds that the VNT turns make me wince when I think of that being abruptly slowed. My CSX had a BOV on it when I bought the car. I've since installed a different one. See pic for how my BOV was mounted on the CSX before I changed it up. I'll post the video of my new turbo installation which shows my new BOV mounting.



    - - - Updated - - -


  3. #3
    We Todd D dot D Turbo Mopar Staff sdac guy's Avatar
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    Re: VNT's and BOV's

    Cordes is correct in what he says, but to go farther and to make it clearer ..

    The VNT does not need a wastegate, which, in stock forms, would be mounted on the turbo controlling the exhaust side. Blow Off Valves are mounted somewhere in the intake stream and vent pressure from the compressor side of the turbo (intake side) back into the intake air stream, or to the atmosphere.

    Do VNT's benefit from the BOV's? Yes they do. While the 1989 Shelby CSX with the VNT motor did not come with a BOV, in 1990, all of the factory VNT cars did have a BOV mounted in the air box. A vent tube was run from the compressor side of the turbo to the bottom of the air box as an input to the BOV.


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  4. #4
    Mitsu booster
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    Re: VNT's and BOV's

    Ahhh I see, it's much clearer now! I've browsed some BOV'S here and there. I'd like something that won't break the bank. What do you guys suggest? Is the eBay Type rs any good?
    Last edited by silverWS6; 04-07-2016 at 01:06 PM.

  5. #5
    Hybrid booster Turbo Mopar Contributor
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    Re: VNT's and BOV's

    In the '90 VNT, there is a BOV built in to the airbox. The '90 VNT airbox is the same as '90 - '92 TI air boxes (some tiny variations). Personally, I love the '90+ stock airbox BOV sound. Unfortunately, the hose set from the '90 VNT is difficult to find. Also, it doesn't work with a K&N cone (or cylindrical) filter.

    There was a tiny BOV used in '88 - '89 air boxes in TI cars and TIII cars. If you're looking for the stealthy stock look, it's worth a try, but is pretty crappy. It works fine for stock boost levels, I guess. It's definitely the choice for the most "budget conscious" as you can probably get one for free.

  6. #6
    Mitsu booster
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    Re: VNT's and BOV's

    Quote Originally Posted by Turbo SOB View Post
    In the '90 VNT, there is a BOV built in to the airbox. The '90 VNT airbox is the same as '90 - '92 TI air boxes (some tiny variations). Personally, I love the '90+ stock airbox BOV sound. Unfortunately, the hose set from the '90 VNT is difficult to find. Also, it doesn't work with a K&N cone (or cylindrical) filter.

    There was a tiny BOV used in '88 - '89 air boxes in TI cars and TIII cars. If you're looking for the stealthy stock look, it's worth a try, but is pretty crappy. It works fine for stock boost levels, I guess. It's definitely the choice for the most "budget conscious" as you can probably get one for free.
    Right now my max boost is 15 psi (14.7). I don't mind having a super loud BOV either

  7. #7
    Hybrid booster
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    Re: VNT's and BOV's

    With, eBay there are good one and bad ones. I would try those that look like a good knock off of a known brand or get the known brand that appears from time to time.

    http://www.ebay.com/sch/i.html?_from...ve&_sacat=6000

  8. #8
    Supporting Member II Turbo Mopar Contributor DOHCRT's Avatar
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    Re: VNT's and BOV's

    Gen 1 Mitsu Eclipse...Quick, Simple, Cheap and holds 18-20psi

    Perfect Turbo Mopar part. All of my car have one...


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